In relatively small turbine engines in airborne environments, fuel flows at high altitudes, particularly during starting of the turbine engine, are frequently quite low. Consequently, fuel injectors requiring high fuel pressures are commonly used to achieve pressure atomization of the fuel.
However, at low turbine speeds, it is difficult with available fuel pumps to generate the necessary fuel pressure. Further, at such low speeds, the engine compressor will not be delivering a large volume of compressed air and the atomization assists resulting from air blast atomization of fuel is unavailable. By way of example, in a typical worst case, the pressure drop across the combustor is about one inch of water which ordinarily is insufficient to provide acceptable fuel atomization.
To meet these difficulties, conventional injectors have extremely small orifices to provide the desired atomization, making them precision formed parts. They are thus costly to manufacture. At the same time, because of the very small orifices employed, they are prone to plugging, a factor that clearly detracts from reliability. Where lower pressure atomizing fuel injectors are used with viscous fuels, high losses occur which reduce atomization efficiency and atomization is frequently unsatisfactory.
In the above identified, co-pending application, a new and improved fuel injector overcoming one or more of the above problems is proposed. At the same time, further improvements are always welcome and the present invention relates to a fuel injector for a gas turbine engine that is improved over the construction disclosed in the copending application as well as a method of fabricating such a fuel injector.